The purpose of this study is to determine whether once weekly azithromycin prevents an opportunistic infection known as Mycobacterium avium complex (MAC) from occurring in persons who have responded to anti-HIV medications. It is well known that persons with less than 50 CD4 cells have a 2 in 5 chance of developing MAC; what is not known is whether someone who initially had a low CD4 count, but has since had an immune response to anti-HIV medication has the same risk. This study is to determine whether once weekly azithromycin is necessary in persons who have had a CD4 count less than 50, but who now have a CD4 count over 100 cells/ul. Currently, it is known that taking new antiretroviral therapies will increase CD4 counts to much higher numbers. If however, the CD4 count becomes very low, subjects are more likely ot develope opportunistic diseases like Mycobacterium avium Complex (MAC)disease. Azithromycin is one of three FDA-approved drugs that has been shown to lower the risk of getting MAC disease in subjects with low CD4 cell counts. Azithromycin is taken oce per week and has fewer sid effects (bad effects) than other drugs to prevent MAC.